<!DOCTYPE html>
<!--
- Copyright (C) 2012 David Geary. This code is from the book
- Core HTML5 Canvas, published by Prentice-Hall in 2012.
-
- License:
-
- Permission is hereby granted, free of charge, to any person
- obtaining a copy of this software and associated documentation files
- (the "Software"), to deal in the Software without restriction,
- including without limitation the rights to use, copy, modify, merge,
- publish, distribute, sublicense, and/or sell copies of the Software,
- and to permit persons to whom the Software is furnished to do so,
- subject to the following conditions:
-
- The above copyright notice and this permission notice shall be
- included in all copies or substantial portions of the Software.
-
- The Software may not be used to create training material of any sort,
- including courses, books, instructional videos, presentations, etc.
- without the express written consent of David Geary.
-
- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
- EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
- OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
- NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
- HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
- WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
- FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
- OTHER DEALINGS IN THE SOFTWARE.
-->

<head>
    <title>Study</title>
</head>

<body>
<canvas id='canvas' width='400' height='400'>
    Canvas not supported
</canvas>

<script>
    var canvas = document.getElementById('canvas'),
        context = canvas.getContext('2d');

    context.beginPath();
    context.rect(10,10,100,100);
    context.stroke();

    //context.beginPath(); //如果没有这句话，那么第一个矩形会被重新绘制一遍，结果就是它的颜色比第二个的更深一点
    context.rect(50,50,100,100);
    context.stroke();
</script>
</body>
</html>
